Optical deflector

ABSTRACT

An optical deflector includes a magnet unit, which generates a magnetic field, and a movable plate unit, which is placed in the magnetic field. The movable plate unit has an inner movable plate having a reflecting surface, an outer movable plate, two inner torsion bars connecting the inner and outer movable plates, a support located outside the outer movable plate, and two outer torsion bars connecting the outer movable plate and support. The movable plate unit has two inner drive wiring portions that extend along by a periphery of the inner movable plate. The magnet unit includes magnets, two adjacent magnets of which are opposite in magnetic polarity direction. The inner drive wiring portions extend almost parallel to boundaries between the two adjacent magnets and are respectively located substantially immediately above the boundaries. Currents of the same direction are applied to the two inner drive wiring portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2003-405787, filed Dec. 4, 2003; and No. 2004-328815, filed Nov. 12, 2004, the entire contents of both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electromagnetically actuated optical deflector.

2. Description of the Related Art

Recently, attention has been paid to an optical deflector manufactured by using a micromachining technique based on a semiconductor manufacturing technique.

The specification of U.S. Pat. No. 6,388,789 discloses, as such an optical deflector, an electromagnetically actuated two-dimensional optical deflector. FIG. 13 is a perspective view of the main part of the optical deflector disclosed in U.S. Pat. No. 6,388,789. FIG. 14 is a sectional perspective view of the optical deflector disclosed in U.S. Pat. No. 6,388,789.

As shown in FIG. 13, this two-dimensional optical deflector includes a first rotating portion 1002, which can rock about the first rotation axis with respect to a support 1001, and a second rotating portion 1003, which can rotate rock the second rotation axis with respect to the first rotating portion 1002. The second rotating portion 1003 has a reflecting surface for reflecting light. The support 1001 and first rotating portion 1002 are coupled to each other through a pair of hinges 1004 and 1004B extending along the first rotation axis. The first rotating portion 1002 and second rotating portion 1003 are coupled to each other through a pair of hinges 1005 and 1005B extending along the second rotation axis.

A pair of first coils 1061 and 1062 for enabling rocking about the first rotation axis and a pair of second coils 1071 and 1072 for enabling rocking about the second rotation axis are formed on the second rotating portion 1003. The first coils 1061 and 1062 are connected to each other through a wiring 1006. The second coils 1071 and 1072 are connected to each other through a wiring 1007. Two wirings 1006A for supplying power to the first coils 1061 and 1062 extend on the pair of hinges 1004 and 1004B, respectively, via the first rotating portion 1002. Likewise, two wirings 1007A for supplying power to the second coils 1071 and 1072 extend on the pair of hinges 1004 and 1004B, respectively, via the first rotating portion 1002.

As shown in FIG. 14, a magnet 1100 is placed below the second rotating portion 1003. The magnet 1100 generates a magnetic field 1089 radially spreading from the center of the second rotating portion 1003 to the support 1001. The second rotating portion 1003 is rocked about the first rotation axis by the interaction between the currents flowing in the first coils 1061 and 1062 and the magnetic field 1089, and also about the second rotation axis by the interaction between the currents flowing in the second coils 1071 and 1072 and the magnetic field 1089.

U.S. Pat. No. 6,404,313 discloses another electromagnetically actuated two-dimensional optical deflector. FIG. 15 is an exploded perspective view of the optical deflector disclosed in U.S. Pat. No. 6,404,313.

As shown in FIG. 15, this two-dimensional optical deflector includes an outer movable plate 2002 located inside a support 2001, an inner movable plate 2003 located inside the outer movable plate 2002, a first torsion bar 2004 supporting the support 2001 so as to allow it to rock about the X-axis with respect to the outer movable plate 2002, and a second torsion bar 2005 supporting the inner movable plate 2003 so as to allow it to rock about the Y-axis with respect to the outer movable plate 2002. The inner movable plate 2003 has a reflecting surface 2104 for reflecting light.

A first driving coil 2102 with a single turn extends on the outer movable plate 2002. A second driving coil 2103 with a single turn extends near a peripheral portion on the inner movable plate 2003. The first driving coil 2102 is connected to the second driving coil 2103.

A pair of magnets 2105 and 2106 are arranged along a diagonal line outside this structure. The magnetic field generated by the magnets 2105 and 2106 exists on one of the diagonal lines. The inner movable plate 2003 is rocked about the X-axis by the interaction between the current flowing in the first driving coil 2102 and the magnetic field, and to rock about the Y-axis by the interaction between the current flowing in the second driving coil 2103 and the magnetic field.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to an electromagnetically actuated two-dimensional optical deflector, which can deflect a light beam about two axes. The optical deflector according to the present invention comprises a magnet unit, which generates a magnetic field, and a movable plate unit, which is placed in the magnetic field. The movable plate unit has an inner movable plate having a reflecting surface, an outer movable plate located outside the inner movable plate, two inner torsion bars connecting the inner movable plate and the outer movable plate, a support located outside the outer movable plate, and two outer torsion bars connecting the outer movable plate and the support. The inner torsion bars extend along a first axis and are capable of twisting about the first axis so as to allow the inner movable plate to tilt about the first axis with respect to the outer movable plate. The outer torsion bars extend along a second axis perpendicular to the first axis and are capable of twisting about the second axis so as to allow the outer movable plate to tilt about the second axis with respect to the support. The movable plate unit further has two inner drive wiring portions that extend along by a periphery of the inner movable plate. The magnet unit includes magnets, two adjacent magnets of which are opposite in magnetic polarity direction. The inner drive wiring portions extend substantially parallel to boundaries between the two adjacent magnets and are respectively located substantially immediately above the boundaries. Currents of the same direction are applied to the two inner drive wiring portions.

The present invention is directed to an electromagnetically actuated one-dimensional optical deflector, which can deflect a light beam only about one axis. The optical deflector according to the present invention comprises a magnet unit, which generates a magnetic field, and a movable plate unit, which is placed in the magnetic field. The movable plate unit has a movable plate having a reflecting surface, a support located outside the movable plate, and two torsion bars connecting the movable plate and the support. The torsion bars extend along one axis and are capable of twisting about the axis so as to allow the movable plate to tilt about the axis with respect to the support. The movable plate unit further has two drive wiring portions that extend along by a periphery of the movable plate. The magnet unit includes magnets, two adjacent magnets of which are opposite in magnetic polarity direction. The drive wiring portions extend substantially parallel to boundaries between the two adjacent magnets and are respectively located substantially immediately above the boundaries. Currents of the same direction are applied to the two inner drive wiring portions.

Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present invention.

FIG. 1 is a sectional perspective view of an optical deflector according to the first embodiment of the present invention;

FIG. 2 is a perspective view of the movable plate unit shown in FIG. 1;

FIG. 3 is a plan view of the movable plate unit shown in FIG. 2;

FIG. 4 is a plan view of the magnet unit shown in FIG. 1;

FIG. 5 is a sectional perspective view of an optical deflector according to the second embodiment of the present invention;

FIG. 6 is a plan view of the magnet unit shown in FIG. 5;

FIG. 7 is a sectional perspective view of an optical deflector according to the third embodiment of the present invention;

FIG. 8 is a plan view of the movable plate unit shown in FIG. 7;

FIG. 9 is a plan view of the magnet unit shown in FIG. 7;

FIG. 10 is a sectional perspective view of an optical deflector according to the fourth embodiment of the present invention;

FIG. 11 is a plan view of the movable plate unit shown in FIG. 10;

FIG. 12 is a plan view of the magnet unit shown in FIG. 10;

FIG. 13 is a perspective view of the main part of the optical deflector disclosed in U.S. Pat. No. 6,388,789;

FIG. 14 is a sectional perspective view of the optical deflector disclosed in U.S. Pat. No. 6,388,789; and

FIG. 15 is an exploded perspective view of the optical deflector disclosed in U.S. Pat. No. 6,404,313.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention will be described below with reference to the views of the accompanying drawing.

First Embodiment

FIG. 1 is a sectional perspective view of an optical deflector according to the first embodiment of the present invention. FIG. 2 is a perspective view of a movable plate unit shown in FIG. 1. The movable plate unit shown in FIG. 2 is an upside down view of that shown in FIG. 1. FIG. 3 is a plan view of the movable plate unit shown in FIG. 2. FIG. 4 is a plan view of a magnet unit shown in FIG. 1.

As shown in FIG. 1, a two-dimensional optical deflector 100 includes a magnet unit 170, which generates a magnetic field, and a movable plate unit 110 placed in the magnetic field generated by the magnet unit 170. The movable plate unit 110 and magnet unit 170 are arranged at a predetermined interval.

As shown in FIGS. 2 and 3, the movable plate unit 110 includes an inner movable plate 112 in the form of a rectangular plate, an outer movable plate 116 in the form of a rectangular frame located outside the inner movable plate 112, two inner torsion bars (first inner torsion bar 114 a and second inner torsion bar 114 b) connecting the inner movable plate 112 and the outer movable plate 116, a support 120 in the form of a rectangular plate located outside the outer movable plate 116, and two outer torsion bars (first outer torsion bar 118 a and second outer torsion bar 118 b) connecting the outer movable plate 116 and the support 120.

Although the outer movable plate 116 is in the form of a frame surrounding the inner movable plate 112, the form of the outer movable plate 116 is not specifically limited to this. Although the support 120 is in the form of a frame surrounding the outer movable plate 116, the form of the support 120 is not limited to this, and may have another shape such as a U shape. In addition, the support 120 is formed from one member, but may be formed from two members that are spaced apart from each other.

As shown in FIG. 1, the inner movable plate 112 has, on its upper surface, a reflecting surface 122 for reflecting light. The reflecting surface 122 is formed from, for example, a thin gold (Au) film. In this case, the upper surface of the inner movable plate 112 is one of the two largest parallel flat surfaces. Referring to FIG. 1, the upper surface is the one seen and located on the upper side. In addition, referring to FIG. 1, the surface that is located on the lower side and is hidden from the eye will be referred to as a lower surface.

As shown in FIGS. 2 and 3, the two inner torsion bars 114 a and 114 b extend on an almost straight line along a first axis A1. The two outer torsion bars 118 a and 118 b also extend on an almost straight line along a second axis A2. The first and second axes A1 and A2 are almost perpendicular to each other.

The outer peripheral shape of the inner movable plate 112 is rectangular when viewed from above, and two central axes of the rectangle (two axes which pass through the center of the rectangle and are perpendicular to sides of the rectangle), which are perpendicular to each other, are parallel to the first axis A1 and second axis A2, respectively. The outer peripheral shape of the outer movable plate 116 is rectangular when viewed from above, and two central axes of the rectangle (two axes which pass through the center of the rectangle and are perpendicular to sides of the rectangle), which are perpendicular to each other, are also parallel to the first axis A1 and second axis A2.

The outer torsion bars 118 a and 118 b are capable of twisting about the second axis A2 and allow the outer movable plate 116 to tilt about the second axis A2 with respect to the support 120. The inner torsion bars 114 a and 114 b are capable of twisting about the second axis and allow the inner movable plate 112 to rock about the first axis A1 with respect to the outer movable plate 116.

Consequently, the direction of the reflecting surface 122 of the inner movable plate 112 is allowed to be two-dimensionally changed, so that the two-dimensional optical deflector 100 allows a beam of light reflected by the reflecting surface 122 to be deflected.

The movable plate unit 110 is formed from a silicon substrate by using a kind of semiconductor fabrication process. The inner movable plate 112 and outer movable plate 116 are formed from, for example, thin silicon plates obtained by processing a silicon substrate. The inner torsion bars 114 a and 114 b and outer torsion bars 118 a and 118 b are formed from, for example, a thin silicon film or thin polyimide film. The material to be used for the inner movable plate 112, outer movable plate 116, support 120, inner torsion bars 114 a and 114 b, and outer torsion bars 118 a and 118 b may include poly silicon, silicon nitride, an organic material, a metal material, and the like in addition to silicon and polyimide.

As shown in FIG. 3, the movable plate unit 110 further includes two inner wirings (first inner wiring 130 a and second inner wiring 130 b) extending on the inner movable plate 112, inner torsion bars 114 a and 114 b, outer movable plate 116, outer torsion bars 118 a and 118 b, and support 120. The first inner wiring 130 a includes a first inner drive wiring portion 132 a and two first inner extracted wiring portions 134 a and 136 a respectively extending from the two ends of the first inner drive wiring portion 132 a. Likewise, the second inner wiring 130 b includes a second inner drive wiring portion 132 b and two second inner extracted wiring portions 134 b and 136 b respectively extending from the two ends of the second inner drive wiring portion 132 b.

In this case, the inner drive wiring portions 132 a and 132 b are parts of the inner wirings 130 a and 130 b that actually contribute to the actuation of the inner movable plate 112 and extend parallel to the first axis A1 along by a periphery of the inner movable plate 112. The first inner extracted wiring portions 134 a and 136 a are parts of the first inner wiring 130 a that exclude the first inner drive wiring portion 132 a. Likewise, the second inner extracted wiring portions 134 b and 136 b are parts of the second inner wiring 130 b that exclude the second inner drive wiring portion 132 b.

As is obvious from FIG. 3, the first inner drive wiring portion 132 a and second inner drive wiring portion 132 b are located almost line-symmetrically with respect to the first axis A1.

Referring to FIG. 3, the first inner extracted wiring portion 134 a extending from the left end portion of the first inner drive wiring portion 132 a on the upper side extends downward along by the periphery of the inner movable plate 112, passes through the first inner torsion bar 114 a on the left side, extends upward along by the inner periphery of the outer movable plate 116, passes through the first outer torsion bar 118 a on the upper side, extends to the left on the support 120, and terminates at an electrode pad 144 a provided on the support 120.

The first inner extracted wiring portion 136 a extending from the right end portion of the first inner drive wiring portion 132 a extends downward along by the periphery of the inner movable plate 112, passes through the second inner torsion bar 114 b on the right side, extends upward along by the periphery of the outer movable plate 116, passes through the first outer torsion bar 118 a on the upper side, extends to the right on the support 120, and terminates at an electrode pad 146 a provided on the support 120.

As is obvious from FIG. 3, the first inner extracted wiring portion 134 a and first inner extracted wiring portion 136 a are located almost line-symmetrically with respect to the first axis A1.

The second inner extracted wiring portion 134 b extending from the left end portion of the second inner drive wiring portion 132 b on the lower side extends upward along by the periphery of the inner movable plate 112, passes through the first inner torsion bar 114 a on the left side, extends downward along by the periphery of the outer movable plate 116, passes through the second outer torsion bar 118 b on the lower side, extends to the left on the support 120, and terminates at an electrode pad 144 b provided on the support 120.

The second inner extracted wiring portion 136 b extending from the right end portion of the second inner drive wiring portion 132 b extends upward along by the periphery of the inner movable plate 112, passes through a second inner torsion bar 114 b on the right side, extends downward along by the inner periphery of the outer movable plate 116, passes through the second outer torsion bar 118 b on the lower side, extends to the right on the support 120, and terminates at an electrode pad 146 b provided on the support 120.

As is obvious from FIG. 3, the second inner extracted wiring portion 134 b and second inner extracted wiring portion 136 b are located almost line-symmetrically with respect to the second axis A2.

The movable plate unit 110 further includes two outer wirings (first outer wiring 150 a and second outer wiring 150 b) extending on the outer movable plate 116, outer torsion bars 118 a and 118 b, and support 120. The first outer wiring 150 a includes a first outer drive wiring portion 152 a and two first outer extracted wiring portions 154 a and 156 a respectively extending from the two ends of the first outer drive wiring portion 152 a. Likewise, the second outer wiring 150 b includes a second outer drive wiring portion 152 b and two second outer extracted wiring portions 154 b and 156 b respectively extending from the two ends of the second outer drive wiring portion 152 b.

In this case, the outer drive wiring portions 152 a and 152 b are respectively parts of the outer wirings 150 a and 150 b that actually contribute to the actuation of the outer movable plate 116 and extend parallel to the second axis A2 along by a periphery of the outer movable plate 116. The first outer extracted wiring portions 154 a and 156 a are parts of the first outer wiring 150 a that exclude the first outer drive wiring portion 152 a. Likewise, the second outer extracted wiring portions 154 b and 156 b are parts of the second outer wiring 150 b that exclude the second outer drive wiring portion 152 b.

As is obvious from FIG. 3, the first outer drive wiring portion 152 a and second outer drive wiring portion 152 b are located almost line-symmetrically with respect to the second axis A2.

Referring to FIG. 3, the first outer extracted wiring portion 154 a extending from the upper end portion of the first outer drive wiring portion 152 a on the left side extends to the right along by the outer periphery of the outer movable plate 116, passes through the first outer torsion bar 118 a on the upper side, extends to the left on the support 120, and terminates at an electrode pad 164 a provided on the support 120.

The first outer extracted wiring portion 156 a extending from the lower end portion of the first outer drive wiring portion 152 a extends to the right along by the outer periphery of the outer movable plate 116, passes through the second outer torsion bar 118 b on the lower side, extends to the left on the support 120, and terminates at an electrode pad 166 a provided on the support 120.

As is obvious from FIG. 3, the first outer extracted wiring portion 154 a and first outer extracted wiring portion 156 a are located almost line-symmetrically with respect to the first axis A1.

The second outer extracted wiring portion 154 b extending from the upper end portion of the second outer drive wiring portion 152 b on the right side extends to the left along by the outer periphery of the outer movable plate 116, passes through the first outer torsion bar 118 a on the upper side, extends to the right on the support 120, and terminates at an electrode pad 164 b provided on the support 120.

The second outer extracted wiring portion 156 b extending from the lower end portion of the second outer drive wiring portion 152 b extends to the left along by the outer periphery of the outer movable plate 116, passes through the second outer torsion bar 118 b on the lower side, extends to the right on the support 120, and terminates at an electrode pad 166 b provided on the support 120.

As is obvious from FIG. 3, the second outer extracted wiring portion 154 b and second outer extracted wiring portion 156 b are located almost line-symmetrically with respect to the first axis A1.

Although not specifically shown, the wirings 130 a, 130 b, 150 a, and 150 b are preferably covered with isolation film such as silicon oxide film for electric isolation.

The wirings 130 a, 130 b, 150 a, and 150 b and the electrode pads 144 a, 144 b, 146 a, 146 b, 164 a, 164 b, 166 a, and 166 b are formed from aluminum by using, for example, a semiconductor fabrication process.

For example, the wirings 130 a, 130 b, 150 a, and 150 b and the electrode pads 144 a, 144 b, 146 a, 146 b, 164 a, 164 b, 166 a, and 166 b are formed by forming an aluminum film on the surface of a structure including the inner movable plate 112, outer movable plate 116, support 120, inner torsion bars 114 a and 114 b, and outer torsion bars 118 a and 118 b formed from a silicon substrate using a kind of semiconductor fabrication process as described above, and by patterning the film.

The material to be used for the wirings 130 a, 130 b, 150 a, and 150 b and the electrode pads 144 a, 144 b, 146 a, 146 b, 164 a, 164 b, 166 a, and 166 b may be copper or gold (Au) instead of aluminum, preferably a metal having a low resistivity.

As shown in FIG. 4, a magnet unit 170 includes a magnet 172 located at the center, two magnets 174 a and 174 b located on the two sides of the magnet 172 along the first axis A1, and two magnets 176 a and 176 b located on the two sides of the magnet 172 along the second axis A2. The magnet 172 has an N pole on the side facing the movable plate unit 110. The magnets 174 a and 174 b and the magnets 176 a and 176 b each have an S pole on the side facing the movable plate unit 110. That is, the two adjacent magnets are opposite in magnetic polarity direction. The magnets, 172, 174 a, 174 b, 176 a, and 176 b each have a rectangular parallelepiped shape, and are fixed to each other with an adhesive.

As shown in FIG. 1, the movable plate unit 110 and magnet unit 170 are arranged at a predetermined interval. The inner drive wiring portions 132 a and 132 b extend almost parallel to the boundaries between the magnet 172 and the magnets 174 a and 174 b. Although the second inner drive wiring portion 132 b is not shown in FIG. 1, the positional relationship with the second inner drive wiring portion 132 b can easily be understood by referring to FIGS. 3 and 4. The outer drive wiring portions 152 a and 152 b extend almost parallel to the boundaries between the magnet 172 and the magnets 176 a and 176 b.

The first inner drive wiring portion 132 a is located almost immediately above the boundary between the magnet 172 and the magnet 174 a. The second inner drive wiring portion 132 b is located almost immediately above the boundary between the magnet 172 and the magnet 174 b. The first outer drive wiring portion 152 a is located almost immediately above the boundary between the magnet 172 and the magnet 176 a. The second outer drive wiring portion 152 b is located almost immediately above the boundary between the magnet 172 and the magnet 176 b. In this case, “immediately above” indicates a direction that is perpendicular to both the first and second axes A1 and A2 and extends from the magnet unit 170 to the movable plate unit 110.

In this arrangement relationship, the magnetic flux density near the boundary between two adjacent magnets with opposite magnetic polarity directions is high. That is, the first inner drive wiring portion 132 a is located in a region where the magnetic flux density is high. The second inner drive wiring portion 132 b is located in a region where the magnetic flux density is high. Likewise, the first outer drive wiring portion 152 a is located in a region where the magnetic flux density is high. The second outer drive wiring portion 152 b is located in a region where the magnetic flux density is high.

As shown in FIG. 1, magnetic lines of force flowing from the magnet 172 to the magnet 174 a are almost perpendicular to the boundary between the magnet 172 and the magnet 174 a, and hence cross the first inner drive wiring portion 132 a at almost right angles. Likewise, magnetic lines of force flowing from the magnet 172 to the magnet 174 b are almost perpendicular to the boundary between the magnet 172 and the magnet 174 b, and hence cross the second inner drive wiring portion 132 b at almost right angles. Magnetic lines of force flowing from the magnet 172 to the magnet 176 a are almost perpendicular to the boundary between the magnet 172 and the magnet 176 a, and hence cross the first outer drive wiring portion 152 a at almost right angles. Likewise, magnetic lines of force flowing from the magnet 172 to the magnet 176 b are almost perpendicular to the boundary between the magnet 172 and the magnet 176 b, and hence cross the second outer drive wiring portion 152 b at almost right angles.

The operation of the above optical deflector will be described next.

For example, a drive power supply (not shown) is used to apply a voltage between the electrode pad 164 a and the electrode pad 166 a to cause a current to flow from the electrode pad 164 a to the electrode pad 166 a. In addition, the same voltage is applied between the electrode pad 164 b and the electrode pad 166 b to cause the same current to flow from the electrode pad 164 b to the electrode pad 166 b.

Referring to FIG. 3, a downward current flows in the first outer drive wiring portion 152 a on the outer movable plate 116. The first outer drive wiring portion 152 a is located in outward (leftward) magnetic lines of force, and hence receives the downward Lorentz force in a direction perpendicular to the drawing surface.

Referring to FIG. 3, a downward current flows in the second outer drive wiring portion 152 b on the outer movable plate 116. The second outer drive wiring portion 152 b is located in outward (rightward) magnetic lines of force, and hence receives the upward Lorentz force in the direction perpendicular to the drawing surface.

The outer movable plate 116 therefore receives a couple of forces about the second axis A2, and the outer torsion bars 118 a and 118 b twist. This causes the outer movable plate 116 to tilt about the second axis A2. As a consequence, the inner movable plate 112 tilts about the second axis A2 together with the outer movable plate 116. The tilt angle of the outer movable plate 116 depends on the magnitudes of the currents flowing in the outer drive wiring portions 152 a and 152 b.

For example, a drive power supply (not shown) is used to apply a voltage between the electrode pad 144 a and the electrode pad 146 a to cause a current to flow from the electrode pad 144 a to the electrode pad 146 a. In addition, a voltage is applied between the electrode pad 144 b and the electrode pad 146 b to cause a current to flow from the electrode pad 144 b to the electrode pad 146 b.

Referring to FIG. 3, a rightward current flows in the first inner drive wiring portion 132 a on the inner movable plate 112. The first inner drive wiring portion 132 a is located in outward (upward) magnetic lines of force, and hence receives the upward Lorentz force in the direction perpendicular to the drawing surface.

Referring to FIG. 3, a rightward current flows in the second inner drive wiring portion 132 b on the inner movable plate 112. The second inner drive wiring portion 132 b is located in outward (downward) magnetic lines of force, and hence receives the downward Lorentz force in the direction perpendicular to the drawing surface.

The inner movable plate 112 therefore receives a couple of forces about the first axis A1, and the inner torsion bars 114 a and 114 b twist. This causes the inner movable plate 112 to tilt about the first axis A1. The tilt angle of the inner movable plate 112 depends on the magnitudes of the currents flowing in the inner drive wiring portions 132 a and 132 b.

When the inner movable plate 112 is actuated, the Lorentz force as a force component that causes the outer movable plate 116 to tilt about the second axis A2 is generated in each of parts of the first inner extracted wiring portions 134 a and 136 a that are located on the outer movable plate 116. However, the Lorentz forces received by the first inner extracted wiring portions 134 a and 136 a cancel out each other, so that the forces do not contribute to the tilting of the outer movable plate 116.

More specifically, part of the first inner extracted wiring portion 134 a that is located on the outer movable plate 116 and extends parallel to the second axis A2 receives the downward Lorentz force in the direction perpendicular to the drawing surface. In addition, part of the first inner extracted wiring portion 136 a that is located on the outer movable plate 116 and extends parallel to the second axis A2 receives the downward Lorentz force in the direction perpendicular to the drawing surface. Since the magnitude of the current flowing in the first inner extracted wiring portion 134 a is equal to that of the current flowing in the first inner extracted wiring portion 136 a, the magnitude of the Lorentz force received by the first inner extracted wiring portion 134 a is equal to the magnitude of the Lorentz force received by the first inner extracted wiring portion 136 a.

The Lorentz force received by the first inner extracted wiring portion 134 a and the Lorentz force received by the first inner extracted wiring portion 136 a are both components that causes the outer movable plate 116 to tilt about the second axis A2. However, the two components make the outer movable plate 116 tilt in opposite directions. For this reason, the Lorentz force received by the first inner extracted wiring portion 134 a and that received by the first inner extracted wiring portion 136 a cancel out each other, and hence make substantially no contribution to the tilting of the outer movable plate 116 about the second axis A2.

This equally applies to the second inner extracted wiring portions 134 b and 136 b.

This makes it possible to independently control the tilting of the inner movable plate 112 about the first axis A1 and that about the second axis A2.

More preferably, the magnitude of the current flowing in the first inner wiring 130 a is equal to the magnitude of the current flowing in the second inner wiring 130 b. In this case, currents flow in opposite directions in two parts of the first inner extracted wiring portion 134 a and second inner extracted wiring portion 134 b that are located on the outer movable plate 116 and extend almost parallel to the second axis A2 (located relatively near each other on the left side on the outer movable plate 116). For this reason, the Lorentz forces generated in the respective portions by the interaction with magnetic fields cancel out each other. This also applies to the first inner extracted wiring portion 136 a and second inner extracted wiring portion 136 b. For this reason, the currents that flow in the inner wirings 130 a and 130 b for tilting the inner movable plate 112 have no influence on the tilting of the outer movable plate 116. This makes it possible to independently control the tilting of the inner movable plate 112 about the first axis A1 and that about the second axis A2.

The two-dimensional optical deflector 100 of this embodiment can therefore realize almost completely independent control on the tilting of the inner movable plate 112 about the first axis A1 and that about the second axis A2.

When, for example, the two-dimensional optical deflector 100 is to be used to scan a light beam, AC voltages are applied between the electrode pads 164 a and 166 a and between the electrode pads 164 b and 166 b to make in-phase AC currents flow in the outer wirings 150 a and 150 b. In this case, since the magnitudes of the currents flowing in the first outer drive wiring portions 152 a and 152 b periodically change, the tilt angle of the outer movable plate 116 about the second axis A2 repeatedly changes. That is, the outer movable plate 116 is rocked about the second axis A2. In addition, AC voltages are applied between the electrode pads 144 a and 146 a and between the electrode pads 144 b and 146 b to make AC currents flow in the inner wirings 130 a and 130 b. In this case, since the magnitudes of the currents flowing in the inner drive wiring portions 132 a and 132 b periodically change, the tilt angle of the inner movable plate 112 about the first axis A1 repeatedly changes. That is, the inner movable plate 112 is rocked about the first axis A1. As a consequence, the light beam reflected by the reflecting surface 122 of the inner movable plate 112 is two-dimensionally scanned.

When the two-dimensional optical deflector 100 is to be used to deflect a light beam in a predetermined direction, constant voltages are applied between the electrode pads 164 a and 166 b and between the electrode pads 164 b and 166 b to make DC currents flow in the same direction in the outer wirings 150 a and 150 b. In this case, since the magnitudes of the currents flowing in the outer drive wiring portions 152 a and 152 b are constant, the outer movable plate 116 tilts about the second axis A2 by a predetermined angle. That is, the outer movable plate 116 is deflected about the second axis A2. In addition, DC voltages are applied between the electrode pads 144 a and 146 a and between the electrode pads 144 b and 146 b to make DC currents flow in the inner wirings 130 a and 130 b. In this case, since the magnitudes of the currents flowing in the inner drive wiring portions 132 a and 132 b are constant, the inner movable plate 112 tilts about the first axis A1 by a predetermined angle. That is, the inner movable plate 112 is deflected about the first axis A1. As a consequence, the light beam reflected by the reflecting surface 122 of the inner movable plate 112 is deflected in a predetermined direction.

As is obvious from the above description, the two-dimensional optical deflector 100 of this embodiment can make almost completely independent control on the rocking and deflection of the inner movable plate 112 having the reflecting surface about the first axis A1 and second axis A2. In addition, since the drive wiring portions 132 a, 132 b, 152 a, and 152 b are arranged in the regions where the magnetic flux densities are high, and the magnetic lines of forces generated by the magnet unit 170 cross the drive wiring portions 132 a, 132 b, 152 a, and 152 b at right angles regardless of their positions, the actuation efficiency is high, and the power consumption is low.

According to the above description, currents of the same magnitude are made to flow in the two inner wirings 130 a and 130 b. However, it is not always necessary to make currents of the same magnitude flow in these wirings. The magnitudes of currents to be made to flow in the two inner wirings 130 a and 130 b may differ within the range in which the operation characteristics required for the two-dimensional optical deflector 100 are satisfied. In order to realize independent control suitable for rocking about the first axis A1 and second axis A2, the magnitudes of currents to be made to flow in the two inner wirings 130 a and 130 b are preferably equal to each other.

Although two wirings are provided for each of the inner movable plate 112, outer movable plate 116, and movable plate 212 in this embodiment, one wiring may be provided for each of them. That is, one wiring including two drive wiring portions may be provided for each of the inner movable plate 112, outer movable plate 116, and movable plate 212.

Second Embodiment

This embodiment is directed to another two-dimensional optical deflector. FIG. 5 is a sectional perspective view of the optical deflector according to the second embodiment of the present invention. FIG. 6 is a plan view of a magnet unit in FIG. 5.

The optical deflector of this embodiment differs from that of the first embodiment only in the arrangement of the magnet unit.

As shown in FIG. 5, a two-dimensional optical deflector 100A of this embodiment includes a movable plate unit 110 and magnet unit 180. The movable plate unit 110 is identical to that in the first embodiment. As shown in FIGS. 5 and 6, the magnet unit 180 includes a magnet 182 located at the center and a magnet 184 surrounding the magnet 182. The magnet 182 has an N pole on the side facing the movable plate unit 110. The magnet 184 has an S pole on the side facing the movable plate unit 110. That is, the magnets 182 and 184 are opposite in magnetic polarity direction. The magnet 182 has a rectangular parallelepiped shape. The magnet 184 has a through hole in which the magnet 182 is fitted. The magnet 182 is placed in this through hole. Therefore, the outer peripheral shape of the magnet 182 is rectangular when viewed from above.

As shown in FIG. 5, the movable plate unit 110 and magnet unit 180 are arranged at a predetermined interval. Each of inner drive wiring portions 132 a and 132 b extends almost parallel to the boundary between the magnets 182 and 184 along a first axis. Although the second inner drive wiring portion 132 b is not shown in FIG. 5, the positional relationship with it can be easily understood by referring to FIGS. 3 and 6. Outer drive wiring portions 152 a and 152 b extend almost parallel to the boundaries between the magnets 182 and 184 along a second axis A2.

In addition, the inner drive wiring portions 132 a and 132 b are located almost immediately above the boundary between the magnets 182 and 184 along the first axis A1. The outer drive wiring portions 152 a and 152 b are located almost immediately above the boundary between the magnets 182 and 184 along the second axis A2.

In this arrangement relationship, as in the first embodiment, all the drive wiring portions 132 a, 132 b, 152 a, and 152 b are located in the regions where the magnetic flux densities are high. In addition, the magnetic lines of force passing through the inner drive wiring portions 132 a and 132 b cross them at almost right angles, and the magnetic lines of force passing through the outer drive wiring portions 152 a and 152 b cross them at almost right angles.

In the two-dimensional optical deflector 100A of this embodiment, a magnetic circuit is positioned in accordance with the position of the hole in the magnet 184. This facilitates positioning the magnet 182. Therefore, in addition to the advantages of the first embodiment, positioning of the magnet is facilitated, and the process is simplified.

Third Embodiment

This embodiment is directed to an optical deflector, which one-dimensionally deflects a light beam. FIG. 7 is a sectional perspective view of the optical deflector according to the third embodiment of the present invention. FIG. 8 is a plan view of the movable plate unit shown in FIG. 7. FIG. 9 is a plan view of the magnet unit shown in FIG. 7.

As shown in FIG. 7, an optical deflector 200 includes a magnet unit 270, which generates a magnetic field, and a movable plate unit 210, which is placed in the magnetic field generated by the magnet unit 270. The movable plate unit 210 and magnet unit 270 are arranged at a predetermined interval.

As shown in FIG. 8, the movable plate unit 210 includes a movable plate 212, a support 220 located outside the movable plate 212, and two torsion bars (first torsion bar 218 a and second torsion bar 218 b) connecting the movable plate 212 and the support 220.

The support 220 is in the form of a frame surrounding the movable plate 212. However, the form of the support 220 is not limited to this, and may have another form such as U-shaped form. In addition, the support 220 comprises one member, but may comprise two members spaced apart from each other.

As shown in FIG. 7, the movable plate 212 has, on its upper surface, a reflecting surface 222 for reflecting light. The reflecting surface 222 comprises, for example, a thin gold (Au) film.

As shown in FIG. 8, the two torsion bars 218 a and 218 b extend on an almost straight line along an axis A. The outer peripheral shape of the movable plate 212 is rectangular when viewed from above, and the central axis of the rectangle (the axis that passes through the center of the rectangle and is perpendicular to its side) is parallel to the axis A. The torsion bars 218 a and 218 b are capable of twisting about the axis A so as to allow the movable plate 212 to tilt about the axis A with respect to the support 220.

This makes it possible to one-dimensionally change the direction of the reflecting surface 222 of the movable plate 212. The optical deflector array 200 can therefore one-dimensionally deflect the light beam reflected by the reflecting surface 222.

The movable plate unit 210 is formed from a silicon substrate by using a kind of semiconductor fabrication process. The movable plate 212 is formed from, for example, a thin silicon plate obtained by processing a silicon substrate. The torsion bars 218 a and 218 b are formed from, for example, a thin silicon film or thin polyimide film. The material to be used for the movable plate 212, support 220, and torsion bars 218 a and 218 b may include poly silicon, silicon nitride, an organic material, a metal material, and the like in addition to silicon and polyimide.

As shown in FIG. 8, the movable plate unit 210 further includes two wirings (first wiring 250 a and second wiring 250 b) extending on the movable plate 212, torsion bars 218 a and 218 b, and support 220. The first wiring 250 a includes a first drive wiring portion 252 a and two first extracted wiring portions 254 a and 256 a extending from the two ends of the first drive wiring portion 252 a, respectively. Likewise, the second wiring 250 b includes a second drive wiring portion 252 b and two second extracted wiring portions 254 b and 256 b extending from the two ends of the second drive wiring portion 252 b, respectively.

In this case, the drive wiring portions 252 a and 252 b are parts of the wirings 250 a and 250 b that actually contribute to the actuation of the movable plate 212 and extend parallel to the axis A along by the periphery of the movable plate 212. The first extracted wiring portions 254 a and 256 a are parts of the first wiring 250 a that exclude the first drive wiring portion 252 a. Likewise, the second extracted wiring portions 254 b and 256 b are parts of the second wiring 250 b that exclude the second drive wiring portion 252 b.

As is obvious from FIG. 8, the first drive wiring portion 252 a and second drive wiring portion 252 b are located almost line-symmetrically with respect to the axis A.

Referring to FIG. 8, the first extracted wiring portion 254 a extending from the upper end portion of the first drive wiring portion 252 a on the left side extends to the right along the outer periphery of the movable plate 212, passes through the first torsion bar 218 a on the upper side, extends to the left on the support 220, and terminates at an electrode pad 264 a provided on the support 220.

The first extracted wiring portion 256 a extending from the lower end portion of the first drive wiring portion 252 a, extends to the right along by the outer periphery of the movable plate 212, passes through the second torsion bar 218 b on the lower side, extends to the left on the support 220, and terminates at an electrode pad 266 a provided on the support 220.

The second extracted wiring portion 254 b extending from the upper end portion of the second drive wiring portion 252 b on the right side extends to the left along by the outer periphery of the movable plate 212, passes through the first torsion bar 218 a on the upper side, extends to the right on the support 220, and terminates at an electrode pad 264 b provided on the support 220.

The second extracted wiring portion 256 b extending from the lower end portion of the second drive wiring portion 252 b extends to the left along by the outer periphery of the movable plate 212, passes through the second torsion bar 218 b on the lower side, extends to the right on the support 220, and terminates at an electrode pad 266 b provided on the support 220.

Although not specifically shown, the wirings 250 a and 250 b are preferably covered with isolation film such as silicon oxide film for electric isolation. Materials and forming methods suitable for the wirings 250 a and 250 b and electrode pads 264 a, 264 b, 266 a, and 266 b are the same as those in the first embodiment As shown in FIG. 9, the magnet unit 270 includes a magnet 272 located at the center and two magnets 276 a and 276 b arranged on the two sides of the magnet 272 along a direction perpendicular to the axis A. The magnet 272 has an N pole on the side facing the movable plate unit 210. Each of the magnets 276 a and 276 b has an S pole on the side facing the movable plate unit 210. That is, the magnets 272 and 276 a are opposite in magnetic polarity direction, and the magnets 272 and 276 b are also opposite in magnetic polarity direction. Each of the magnets 272, 276 a, and 276 b has a rectangular parallelepiped shape, and are fixed to each other with an adhesive.

As shown in FIG. 7, the movable plate unit 210 and magnet unit 270 are arranged at a predetermined interval. The drive wiring portions 252 a and 252 b extend almost parallel to the boundaries between the magnets 272, 276 a, and 276 b.

The first drive wiring portion 252 a is placed almost immediately above the boundary between the magnets 272 and 276 a. The second drive wiring portion 252 b is located almost immediately above the boundary between the magnets 272 and 276 b. In this arrangement relationship, as shown in FIG. 7, the magnetic lines of force flowing from the magnet 272 to the magnet 276 a are almost perpendicular to the boundary between the magnet 272 and the magnet 276 a, and hence cross the first drive wiring portion 252 a at almost right angles. Likewise, the magnetic lines of force flowing from the magnet 272 to the magnet 276 b are almost perpendicular to the boundary between the magnet 272 and the magnet 276 b, and hence cross the second drive wiring portion 252 b at almost right angles.

The movable plate in the optical deflector according to this embodiment is actuated in the same manner as the outer movable plate in the two-dimensional optical deflector according to the first embodiment.

When, for example, the optical deflector 200 is to be used to scan a light beam, AC voltages are applied between the electrode pads 264 a and 266 a and between the electrode pads 264 b and 266 b to make in-phase AC currents flow in the wirings 250 a and 250 b. In this case, since the magnitudes of the currents flowing in the drive wiring portions 252 a and 252 b periodically change, the tilt angle of the movable plate 212 about the axis A repeatedly changes. That is, the movable plate 212 is rocked about the axis A. As a consequence, the light beam reflected by the reflecting surface 222 of the movable plate 212 is one-dimensionally scanned.

When the optical deflector 200 is to be used to deflect a light in a predetermined direction, constant voltages are applied between the electrode pads 264 a and 266 a and between the electrode pads 264 b and 266 b to make DC currents flow in the same direction in the wirings 250 a and 250 b. In this case, since the magnitudes of the currents flowing in the drive wiring portions 252 a and 252 b are constant, the movable plate 212 tilts about the axis A by a predetermined angle. That is, the movable plate 212 is deflected about the axis A. That is, the movable plate 212 is deflected about the axis A. As a consequence, the light beam reflected by the reflecting surface 222 of the movable plate 212 is deflected in a predetermined direction.

As is obvious from the above description, in the optical deflector 200 of this embodiment, since the drive wiring portions 252 a and 252 b are arranged in the regions where the magnetic flux densities are high, and the magnetic lines of forces generated by the magnet unit 170 cross the drive wiring portions 252 a and 252 b at almost right angles regardless of their positions, the actuation efficiency is high, and the power consumption is low.

According to this embodiment, the magnet unit 270 comprises the three magnets 272, 276 a, and 276 b arranged along a direction perpendicular to the axis A. However, as in the second embodiment, the magnet unit 270 may comprise one magnet and another magnet surrounding it.

Fourth Embodiment

This embodiment is directed to another two-dimensional optical deflector. FIG. 10 is a sectional perspective view of an optical deflector according to the fourth embodiment. FIG. 11 is a plan view of the movable plate unit shown in FIG. 10. FIG. 12 is a plane view of the magnet unit shown in FIG. 10.

As shown in FIG. 10, a two-dimensional optical deflector 300 of this embodiment includes a movable plate units 310 and magnet unit 380. The movable plate units 310 and magnet unit 380 are arranged at a predetermined interval, and the movable plate units 310 is located within the magnetic field generated by the magnet unit 380.

As shown in FIGS. 10 and 11, the movable plate units 310 includes an inner movable plate 312 in the form of a circular plate, an outer movable plate 316 in the form of a circular frame, which is located outside the inner movable plate 312, two inner torsion bars (first inner torsion bar 314 a and second inner torsion bar 314 b) connecting the inner movable plate 312 and the outer movable plate 316, a support 320 in the form of a rectangular frame, which is located outside the outer movable plate 316, and two outer torsion bars (first outer torsion bar 318 a and second outer torsion bar 318 b) connecting the outer movable plate 316 and the support 320.

As shown in FIG. 10, the inner movable plate 312 has, on its upper surface, a reflecting surface 322 for reflecting light.

As shown in FIGS. 10 and 11, both the two inner torsion bars 314 a and 314 b extend on an almost straight line along a first axis A1. The two outer torsion bars 318 a and 318 b extend on an almost straight line along a second axis A2. The first axis A1 and second axis A2 are almost perpendicular to each other.

The outer peripheral shape of the inner movable plate 312 is circular when viewed from above, and two central axes of the circle, which are perpendicular to each other, are parallel to the first axis A1 and second axis A2, respectively. The outer peripheral shape of the outer movable plate 316 is also circular when viewed from above, and two central axes of the circle, which are perpendicular to each other, are also parallel to the first axis A1 and second axis A2.

The outer peripheral shape of the inner movable plate 312 may be elliptic. In this case, the two central axes (the major and minor axes of the ellipse) of the ellipse, which are perpendicular to each other, are preferably parallel to the first and second axes A1 and A2, respectively. The outer peripheral shape of the outer movable plate 316 may be elliptic. In this case, the two central axes (the major and minor axes of the ellipse) of the ellipse, which are perpendicular to each other, are preferably parallel to the first and second axes A1 and A2, respectively.

In other words, if a circle is regarded as an ellipse in a broad sense, both the outer peripheral shape of the inner movable plate 312 and that of the outer movable plate 316 are elliptic.

The outer torsion bars 318 a and 318 b are capable of twisting and distorting about the second axis A2, thereby enabling the outer movable plate 316 to tilt about the second axis A2 with respect to the support 320. The inner torsion bars 314 a and 314 b are capable of twisting and distorting about the first axis A1, thereby enabling the inner movable plate 312 to tilt about the first axis A1 with respect to the outer movable plate 316.

This makes it possible to two-dimensionally change the direction of the reflecting surface 322 of the inner movable plate 312. The two-dimensional optical deflector 300 can therefore two-dimensionally deflect the light beam reflected by the reflecting surface 322.

As shown in FIG. 11, the movable plate units 310 further includes two inner wirings (first inner wiring 330 a and second inner wiring 330 b) extending on the inner movable plate 312, inner torsion bars 314 a and 314 b, outer movable plate 316, outer torsion bars 318 a and 318 b, and support 320. The first inner wiring 330 a includes a first inner drive wiring portion 332 a and two first inner extracted wiring portions 334 a and 336 a extending from the two ends of the first inner drive wiring portion 332 a, respectively. Likewise, the second inner wiring 330 b includes a second inner drive wiring portion 332 b and two second inner extracted wiring portions 334 b and 336 b extending from the two ends of the second inner drive wiring portion 332 b.

In this case, the inner drive wiring portions 332 a and 332 b are parts of the inner wirings 330 a and 330 b that are located near peripheral portions on the inner movable plate 312 and extend along by the periphery of the inner movable plate 312. The first inner extracted wiring portions 334 a and 336 a are parts of the first inner wiring 330 a that exclude the first inner drive wiring portion 332 a. Likewise, the second inner extracted wiring portions 334 b and 336 b are parts of the second inner wiring 330 b that exclude the second inner drive wiring portion 332 b.

As is obvious from FIG. 11, the first inner drive wiring portion 332 a and second inner drive wiring portion 332 b are located almost line-symmetrically with respect to the first axis A1.

Referring to FIG. 11, the first extracted wiring portion 334 a extending from the left end portion of the first inner drive wiring portion 332 a on the upper side passes through the first inner torsion bar 314 a on the left side, extends upward along by the inner periphery of the outer movable plate 316, passes through the first outer torsion bar 318 a on the upper side, extends to the left on a support 320, and terminates at a electrode pad 344 a provided on the support 320.

The first extracted wiring portion 336 a extending from the right end portion of the first inner drive wiring portion 332 a passes through the second inner torsion bar 314 b on the right side, extends upward along by the inner periphery of the outer movable plate 316, passes through the first outer torsion bar 318 a on the upper side, extends to the right on the support 320, and terminates at an electrode pad 346 a provided on the support 320.

As is obvious from FIG. 11, the first extracted wiring portion 334 a and first extracted wiring portion 336 a are located almost line-symmetrically with respect to the second axis A2.

The second extracted wiring portion 334 b extending from the left end portion of the second inner drive wiring portion 332 b on the lower side passes through the first inner torsion bar 314 a on the left side, extends downward along by the inner periphery of the outer movable plate 316, passes through the second outer torsion bar 318 b on the lower side, extends to the left on the support 320, and terminates at an electrode pad 344 b provided on the support 320.

The second extracted wiring portion 336 b extending from the right end portion of the second inner drive wiring portion 332 b passes through the second inner torsion bar 314 b on the right side, extends downward along by the inner periphery of the outer movable plate 316, passes through the second outer torsion bar 318 b on the lower side, extends to the right on the support 320, and terminates at an electrode pad 346 b provided on the support 320.

As is obvious from FIG. 11, the second extracted wiring portion 334 b and second extracted wiring portion 336 b are located almost line-symmetrically with respect to the second axis A2.

The movable plate units 310 further includes two outer wirings (first outer wiring 350 a and second outer wiring 350 b) extending on the outer movable plate 316, outer torsion bars 318 a and 318 b, and support 320. The first outer wiring 350 a includes a first outer drive wiring portion 352 a and two first outer extracted wiring portions 354 a and 356 a extending from the two ends of the first outer drive wiring portion 352 a, respectively. Likewise, the second outer wiring 350 b includes a second outer drive wiring portion 352 b and two second outer extracted wiring portions 354 b and 356 b extending from the two ends of the second outer drive wiring portion 352 b, respectively.

In this case, the outer drive wiring portions 352 a and 352 b are parts of the outer wirings 350 a and 350 b that extend along by the periphery of the outer movable plate 316. The first outer extracted wiring portions 354 a and 356 a are parts of the first outer wiring 350 a that exclude the first outer drive wiring portion 352 a. Likewise, the second outer extracted wiring portions 354 b and 356 b are parts of the second outer wiring 350 b that exclude the second outer drive wiring portion 352 b.

As is obvious from FIG. 11, the first outer drive wiring portion 352 a and second outer drive wiring portion 352 b are located almost line-symmetrically with respect to the second axis A2.

Referring to FIG. 11, the first outer extracted wiring portion 354 a extending from the upper end portion of the first outer drive wiring portion 352 a on the left side passes through the first outer torsion bar 318 a on the upper side, extends to the left on the support 320, and terminates at an electrode pad 364 a provided on the support 320.

The first outer extracted wiring portion 356 a extending from the lower end portion of the first outer drive wiring portion 352 a passes through the second outer torsion bar 318 b on the lower side, extends to the left on the support 320, and terminates at an electrode pad 366 a provided on the support 320.

As is obvious from FIG. 11, the first outer extracted wiring portion 354 a and first outer extracted wiring portion 356 a are located almost line-symmetrically with respect to the first axis A1.

The second outer extracted wiring portion 354 b extending from the upper end portion of the second outer drive wiring portion 352 b on the right side passes through the first outer torsion bar 318 a on the upper side, extends to the right on the support 320, and terminates at an electrode pad 364 b provided on the support 320.

The second outer extracted wiring portion 356 b extending from the lower end portion of the second outer drive wiring portion 352 b passes through the second outer torsion bar 318 b on the lower side, extends to the right on the support 320, and terminates at an electrode pad 366 b provided on the support 320.

As is obvious from FIG. 11, the second outer extracted wiring portion 354 b and second outer extracted wiring portion 356 b are located almost line-symmetrically with respect to the first axis A1.

Although not specifically shown, the wirings 330 a, 330 b, 350 a, and 350 b are covered with isolation film such as silicon oxide film for electric isolation.

As shown in FIG. 12, the magnet unit 380 includes a magnet 382 located at the center and a magnet 384 surrounding the magnet 382. The magnet 382 has an N pole on the side facing the movable plate units 310, and the magnet 384 has an S pole on the side facing the movable plate units 310. That is, the magnets 382 and 384 are opposite in magnetic polarity direction. The magnet 382 has an elliptic cylindrical shape. The magnet 384 has a through hole in which the magnet 382 is fitted. The magnet 382 is placed in this though hole. Therefore, the outer peripheral shape of the magnet 382 is elliptic when viewed from the above.

Parts of the boundary between the magnets 382 and 384 that extend along the minor axis of the elliptic shape of the magnet 382 are located almost immediately below the inner drive wiring portions 332 a and 332 b, respectively. In addition, parts of the boundary between the magnets 382 and 384 that extend along the major axis of the elliptic shape of the magnet 382 are located almost immediately below the outer drive wiring portions 352 a and 352 b, respectively.

The magnetic flux density near the boundary between the magnets 382 and 384, which are opposite in magnetic polarity direction, is high. For this reason, both portions near the middles of the inner drive wiring portions 332 a and 332 b (portions relatively near the second axis A2) and portions near the middles of the outer drive wiring portions 352 a and 352 b (portions relatively near the first axis A1) are located in regions where the magnetic flux densities are high.

As shown in FIG. 10, the magnetic lines of force flowing from the magnet 382 to the magnet 384 cross the portions near the middles of the inner drive wiring portions 332 a and 332 b and the portions near the middles of the outer drive wiring portions 352 a and 352 b at almost right angles.

In this embodiment, the inner movable plate 312 is actuated about the first axis A1 in the same manner as in the first embodiment except that the magnitudes of Lorentz forces received by the inner drive wiring portions 332 a and 332 b when currents flow in the inner wirings 330 a and 330 b depend on positions. The Lorentz force forces received by the inner drive wiring portions 332 a and 332 b are highest near the middles of the wiring portions, and the Lorentz forces received by parts of the inner drive wiring portions 332 a and 332 b that are near their middles contribute most to the actuation of the inner movable plate 312.

In addition, the outer movable plate 316 is actuated about the second axis A2 in the same manner as in the first embodiment except that the magnitudes of Lorentz forces received by the outer drive wiring portions 352 a and 352 b when currents flow in the outer wirings 350 a and 350 b depend on positions. The Lorentz force forces received by the outer drive wiring portions 352 a and 352 b are highest near the middles of the wiring portions, and the Lorentz forces received by parts of the outer drive wiring portions 352 a and 352 b that are near their middles contribute most to the actuation of the outer movable plate 316.

In the two-dimensional optical deflector 300 of this embodiment, since the inner movable plate 312 is in the form of a circular plate, its inertia moment is smaller than that of a movable plate in the form of a rectangular plate (i.e., the inner movable plate 112 in the first embodiment). In addition, since the outer movable plate 316 is in the form of a circular frame, its inertia moment is smaller than that of a movable plate in the form of a rectangular frame (i.e., the outer movable plate 116 in the first embodiment). This allows the spring stiffness of the inner torsion bars 314 a and 314 b and outer torsion bars 318 a and 318 b to be reduced with the resonant frequency maintained, so that actuating operation with small currents, i.e., a reduction in power consumption is realized.

In this embodiment, each of the inner wirings 330 a and 330 b makes a half turn on the inner movable plate 312. However, each wiring may make more turns. Likewise, each of the outer wirings 350 a and 350 b makes a half turn on the outer movable plate 316. However, each wiring may make more turns.

Although the embodiments of the present invention have been described with reference to the views of the accompanying drawing, the present invention is not limited to these embodiments, and various modifications and changes thereof can be made within the spirit and scope of the invention.

Each embodiment described above is directed to a two-dimensional unit optical deflector. However, such deflectors may be properly arranged into an array.

In the first embodiment, the magnet unit includes five magnets. In the third embodiment, the magnet unit includes three magnets. However, the number of magnets constituting the magnet unit is not limited to them as long as the boundary between two magnets that are opposite in magnetic polarity direction and adjacent to each other is placed almost parallel almost immediately below the drive wiring portion.

Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. 

1. An electromagnetically actuated optical deflector comprising: a magnet unit, which generates a magnetic field; and a movable plate unit, which is placed in the magnetic field, the movable plate unit having an inner movable plate having a reflecting surface, an outer movable plate located outside the inner movable plate, two inner torsion bars connecting the inner movable plate and the outer movable plate, a support located outside the outer movable plate, and two outer torsion bars connecting the outer movable plate and the support, the inner torsion bars extending along a first axis and being capable of twisting about the first axis so as to allow the inner movable plate to tilt about the first axis with respect to the outer movable plate, the outer torsion bars extending along a second axis perpendicular to the first axis and being capable of twisting about the second axis so as to allow the outer movable plate to tilt about the second axis with respect to the support, the movable plate unit further having two inner drive wiring portions that extend along by a periphery of the inner movable plate, and the magnet unit including magnets, two adjacent magnets of the magnets being opposite in magnetic polarity direction, the inner drive wiring portions extending substantially parallel to boundaries between the two adjacent magnets and being respectively located substantially immediately above the boundaries, and currents of the same direction being applied to the two inner drive wiring portions; wherein the movable plate unit further has two outer drive wiring portions that extend along by a periphery of the outer movable plate, the outer drive wiring portions extending substantially parallel to boundaries between the two adjacent magnets and being respectively located substantially immediately above the boundaries, currents of the same direction being applied to the two outer drive wiring portions to apply a driving force to the outer movable plate, the two outer drive wiring portions being provided independently of each other such that they are electrically isolated from each other.
 2. A deflector according to claim 1, wherein an outer peripheral shape of the inner movable plate is a rectangular shape, and two central axes of the rectangular shape, which are perpendicular to each other, are parallel to the first and second axes, respectively.
 3. A deflector according to claim 1, wherein an outer peripheral shape of the outer movable plate is a rectangular shape, and two central axes of the rectangular shape, which are perpendicular to each other, are parallel to the first and second axes, respectively.
 4. A deflector according to claim 1, wherein the two inner drive wiring portions are located substantially line-symmetrically with respect to the first axis and the two outer drive wiring portions are located substantially line-symmetrically with respect to the second axis.
 5. A deflector according to claim 4, wherein the magnet unit includes a magnet located at the center, two magnets arranged at two sides of the magnet along the first axis, and two magnets arranged at two sides of the magnet along the second axis.
 6. A deflector according to claim 1, wherein the two inner drive wiring portions are formed from a single layer at least on the inner movable plate.
 7. A deflector according to claim 1, wherein the inner drive wiring portions on the inner movable plate and the outer drive wiring portions on the outer movable plate are formed from a single layer. 